From de1336faddbdffc8fb4f58af3597d3f031e2b2d9 Mon Sep 17 00:00:00 2001
From: Mitchell Hashimoto <m@mitchellh.com>
Date: Sun, 9 Aug 2026 15:44:25 -0700
Subject: [PATCH] renderer/metal: warm up command queue and shader pipelines

Extend the Metal portion of the startup warmup thread to also create
(and discard) a command queue and build (and discard) the shader
pipelines for both pixel formats we may use (which one is used
depends on the blending config). The first command queue for a device
and the first render pipeline state creations pay one-time driver
setup and shader compilation costs; once warm, the real creations
during surface initialization hit driver and OS caches.

Measured on macOS (Apple Silicon) with local timing instrumentation
during app launch, first surface renderer initialization:

  queue creation:  717us -> 93us
  pipeline builds: 1023us -> 347us
  renderer init total: 2777us -> 1466us
---
 src/renderer/Metal.zig | 29 ++++++++++++++++++++++++++++-
 1 file changed, 28 insertions(+), 1 deletion(-)

diff --git a/src/renderer/Metal.zig b/src/renderer/Metal.zig
index 1ad6b812b..7b59ce500 100644
--- a/src/renderer/Metal.zig
+++ b/src/renderer/Metal.zig
@@ -421,7 +421,34 @@ pub inline fn beginFrame(
 /// one-time cost.
 pub fn warmup() void {
     const device = chooseDevice() catch return;
-    device.release();
+    defer device.release();
+
+    // Create and release a command queue. The first command queue
+    // created for a device pays additional one-time driver setup
+    // costs; subsequent creations are much cheaper.
+    const queue = device.msgSend(objc.Object, objc.sel("newCommandQueue"), .{});
+    queue.release();
+
+    // Build and discard our shader pipelines for both pixel formats we
+    // may use (which one is used depends on the blending config). The
+    // first pipeline state creation compiles shaders which is slow;
+    // once warm, later creations hit driver and OS caches.
+    inline for (.{
+        mtl.MTLPixelFormat.bgra8unorm_srgb,
+        mtl.MTLPixelFormat.bgra8unorm,
+    }) |format| {
+        if (shaders.Shaders.init(
+            std.heap.c_allocator,
+            device,
+            &.{},
+            format,
+        )) |s| {
+            var s_mut = s;
+            s_mut.deinit(std.heap.c_allocator);
+        } else |err| {
+            log.warn("metal warmup shader init failed err={}", .{err});
+        }
+    }
 }
 
 fn chooseDevice() error{NoMetalDevice}!objc.Object {